title: Postantibiotic suppression of bacterial growth.
abstract: Persistent suppression of bacterial growth following exposure of both gram-positive and gram-negative bacteria to numerous antimicrobial agents was studied. The persistent, or postantibiotic, effect was quantitated by periodic counts of colony-forming units after removal of the drug by washing, dilution, or inactivation with penicillinase. Although a postantibiotic effect was observed with all drugs studied, there were marked differences among drugs in their postantibiotic effects on certain organisms. With gram-positive organisms, concentrations of beta-lactam antibiotics near the minimal inhibitory concentration produced persistent effects lasting 1-3 hr. With gram-negative organisms much higher concentrations were required to elicit a postantibiotic effect. Inhibitors of protein and RNA synthesis produced the longest persistent suppression of growth, which was of comparable duration in gram-positive and gram-negative bacteria. Only a short persistent effect of gentamicin was observed with Staphylococcus aureus and Escherichia coli, but a postantibiotic effect lasting 1.6-2.6 hr was observed with Pseudomonas aeruginosa. The duration of the postantibiotic effect was related linearly to concentration of drug and duration of exposure up to a point of maximal response. Persistent effects following exposure to antibiotics were also demonstrated in 90% human serum.
mesh_terms: D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D001682:Biological Availability; D004305:Dose-Response Relationship, Drug; D004917:Erythromycin / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects; D005839:Gentamicins / Q000008:administration & dosage / Q000494:pharmacology; D007711:Klebsiella pneumoniae / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D010406:Penicillins / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology; D011513:Proteus mirabilis / Q000187:drug effects; D011550:Pseudomonas aeruginosa / Q000187:drug effects; D013211:Staphylococcus aureus / Q000187:drug effects; D013296:Streptococcus pneumoniae / Q000187:drug effects; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D005839:Gentamicins; D010406:Penicillins; D004917:Erythromycin